Many attempts have been made in the prior art to provide adequate storage for digitized images in data processing systems. Early prior art techniques were based upon the conversion of photographic microfiche records into digitized images which were then stored on either magnetic tape or magnetic disks for later retrieval and display. The problem with the early prior art was that since the digitized image records were quite large, they required substantial quantities of storage and this limited the appeal of such systems for practical applications.
As the prior art evolved, digital image compression algorithms were developed to convert the digitized bit patterns for the images into a more compressed record, which could be more conveniently stored on magnetic tape or magnetic disk devices. However, the size of these compressed records was still large enough to present a problem in providing adequate storage within a digital image storage system. In addition, because of the size of the compressed records, access times on the magnetic tape or magnetic disk storage devices was unacceptably long.
The prior art has failed to provide a digital image storage system which will provide a fast access time for either magnetic or optical disk storage, will have a minimized communications traffic on the communications networks used by the image storage system, and yet will maintain the availability of high resolution images for occasional high resolution requirements.